I’m a huge fan of the "Come grow old with me! The best is yet to be. The last of life for which the first was made." (Robert Browning). Tho I really prefer it with just the first two lines. Much love for that one.

So, totally cheesy, but, I love this one from the always classic Shakespeare: "Love is not love which alters when it alteration finds, or bends with the remover to remove. Oh no, it is an ever fixed mark, that looks on tempests and is never shaken."